High frequency valve



sept 9, l969 .1. c. BooNsHAFT ETAL 3,466,003

HIGH FREQUENCY VALVE Filed Dec. 30, 1966 ATTORNEYS United States Patent C U.S. Cl. 251-30 8 Claims ABSTRACT F THE DISCLOSURE A high frequency spool valve comprising a fixed flux electromagnet in the form of an annulus. A stem having a screw, spring and body portion joined together is disposed within the annulus with a yoke adjustably fixed to one end of the stem and to the other end of the stem affixed to the electromagnet. A valve spool and a plurality of channels and lines are disposed within the annulus. The spring is unstressed whenr'the spool is in a neutral position; exerts tension force when the spool is in a position on one side of neutral and an equal compressive force when the spool is on the other side of neutral.

This invention ralates to a valve. More particularly, it relates to an hydraulic valve capable of very high frequency of operation in response to an electrical signal.

This invention has particular applicability as a pilot valve, serving as the first stage of a two-stage servo valve.

It has been known to provide two-stage servo valves in which the first stage is a pilot valve response to electrical signals and the second stage is an operating valve which is controlled by the output of the pilot valve. In such a two-stage servo valve, the operating valve has a greater flow capacity than the pilot valve. It is a desirable characteristics of such two-stage valves to have as high a frequency of operation as can be obtained.

The present invention contemplates what may be described as a single stage servo valve suitable for use as the first stage of a two stage valve. It is characteristic of the present invention to have a higher frequency than is available in other known valves of the same general class of service, and to be so arranged as to be able to cooperate with a second stage valve in a manner to maximize the overall frequency of the two stage valve.

It is an object of this invention to provide a high frequency valve. Y

It is another object of this invention to provide a high frequency hydraulic valve of simple construction and low current consumption.

It is another object of this invention to provide a high frequency hydraulic servo valve to respond to electrical signals, and to provide relatively low flow capacity at high pressures.

It is yet another object of this invention to provide a high frequency hydraulic servo pilot valve of simple construction, low current consumption, relatively low ow capacity, adapted to be coupled to an operating valve to obtain the maximum frequency of operation available in said operating valve.

It is yet another object of this invention to provide a high frequency servo hydraulic fluid switching deivce suitable as a pilot valve or to operate a shaker.

Other aims and objects of this invention are made apparent in the following specification and claims.

The invention is best understood in connection with the accompanying drawings in which like reference numetals refer to like parts, and in which:

FIGURE 1 is an elevational. sectional view taken along the diameter of the valve; and

V'ice FIGURE 2 is a perspective view of the valve stem and parts attached thereto.

The high frequency valve is generally designated 200. A main body or case 30 encloses the central portion of the valve 200. A cap member 40 encloses one end of the valve, and a coupling member 20 comprises the major portion of the other end of the valve.

It is understood that FIGURE 1 is a longitudinal crosssection taken along the diameter of the valve 200. The valve is preferably circular in transverse cross-section, as far as its operating elements go. FIGURE 2 illustrates vthe transverse shape of the valve elements. In practice, it is possible to make the outward appearance of the valve rectangular in transverse corss-section but this external shape involves only the external contours of the members 20, 30 and 40, and does not affect the operting structure or function of the valve.

A fixed flux magnet 32 is provided. This is an angular magnet and is contained within the main body 30. A steady voltage is maintained at all times in magnet 32. It is desirable to produce a steady high flux density from this magnet. The exact specifications of magnet 32 are not essential, but it may preferably draw a current substantially in excess of one ampere. In general, the stronger the fixed flux the better, and the density of the flux is limited by current drain, heat, physical size, and economics.

A variable fiux magnet 33 is provided. This is also in the shape of an annulus. However, the variable flux magnet 33 is part of the moving structure, and it is highly desirable Ito minimize the weight of the variable flux magnet 33 to minimize the inertial effects. The flux density of variable flux magnet 33 is thus much less than that of the xed magnet 32. There is no exact critical specification for magnet 33, but typically it may operate at 28 volts DC. and draw substantially less than one ampere of current.

An electrical connector 45 is provided which introduces leads 46 which connects to fixed flux magnet 32 and leads 47 which connect to variable flux magnet 33. The cap member 40 is provided with a chamber 45a to receive electrical connector 45. An annular seal 44 is provided around connector 45 where it enters cap 40. The connector 45 is held to the cap 40 by any convenient means, and seal 44 prevents the escape of oil or other hydraulic Huid from the interior of the valve. Leads 47 do not go directly to magnet 33, but are brought to connector 47a which is mounted on yoke 70, described below, and thence are conducted to the magnet 33. Fixed flux magnet 32 is at least partially enclosed with a magnetically permeable cover 32a. The magnet 32 is conveniently held in place within case 30 by means of adhesive filler material 34.

The coupling member 20 is held to the main body or case 30 by means of bolts 21. The cap 40 may be similarly fastened to case 30 by means of bolts, which do not show in FIGURE 1, because they lie along another diameter. Annular seals 41 and 42 are provided between cap 40 and body member 30 to prevent the escape of oil from the interior of the valve.

Variable flux magnet 33 is carried on a yoke 70. The general structure of yoke 70 is understood in connection with both FIGURES 1 and 2. It may be described as a generally funnel-shaped member. FIGURE 1 is a view taken along one diameter thereof while FIGURE 2 shows a perspective view of the yoke as it would be seen generally from the direction of cap 40. As shown in both figures, magnet 33 is affixed to the rim of the yoke at its wide mouth. Yoke 70 includes the conical portion 72 and the hollow shaft portion 71. The conical portion 72 is provided with a plurality of holes 72a. These holes existto reduce the weight of the yoke and also to facilitate its movement through oil. Only representative holes 72a are shown in the figures; in practice, it is preferable to have more holes and have them closer together, and representative holes are shown for convenience in illustration. The exact nature, number, and size of these holes are not critical.

The yoke 70 is supported on stem 80; the means of its support permits a very line adjustment of the location of the yoke longitudinally with respect to the stem. The interior of hollow shaft 71 is threaded and the exterior of insert 85 is also threaded so that there are a set of engaging threads 85a between the insert 85 and the shaft 71. The insert 85 is in turn carried on one end of the stem 80'.

The stem 80 comprises four portions; a first threaded portion 81, a spring portion 82, a body portion 83, and a second threaded portion 84. These portions of stern 80 are arranged in the order set forth above. The body portion 83 is provided with a longitudinally extended groove or slot 83a for keying purposes, as is described below.

The insert 85, in addition to its external threads, is provided with a hollow interior also threaded, these interior threads engage the threaded portion 84 of the stem 80. Insert 85 is provided with means to rotate it with respect to both stem 80 and shaft 71. This means it is here shown as a slot on the end of the insert, suitable to receive a screwdriver blade. A set screw 75 is provided through shaft 71 so that the insert 85 may be selectively locked in place against rotation when the proper adjustment has been made.

The irst threaded portion 81 of stem 80 is threaded into the coupling member as shown. When stem 80 has been threaded into the coupling member 20 to a proper desired distance, it is secured in place against rotation or further movement by any convenient means. Preferably, this is accomplished by a set screw extending from the exterior of the coupling member to the stem. This set screw is not shown in the drawing since it lies on a diierent diameter than the one shown.

With stem 80 located with respect to coupling member 20 as described, the fine adjustment of the longitudinal position of the yoke may be made. The arrangement of the internal and external threads on insert 85 make a very tine adjustment possible. If insert 85 is rotated so that it advances on stem 80, it is apparent that yoke 72 would similarly advance if it rotated with the insert. The pitch of the external threads 85a are so related to the interal threads that if insert 85 is rotated to advance on stem 80 and yoke 72 is held against rotation, the threads 85a.' cause the yoke to move away from the stem. In rnaking the line adjustment, the yoke is held against rotation, the stem is held against rotation as described above, and slotted insert 85 is rotated. There is a diierence between the degree of pitch on the internal and external threads of the insert so that for a given rotation, the longitudinal distance that the yoke is carried toward the stem by one set of threads is diiferent than the longitudinal distance that the yoke is carried away from the stem by the other set of threads. Thus, the differential pitch of the internal and external threads of insert 85 results in what may be termed a Vernier adjustment attainable by rotation of the insert.

As has been described, the stem 80 includes a spring portion 82. This spring portion 82 is a machine screw which is machined directly out of the integral stock of stem 80. The purpose of this type of construction is explained below. The body portion 83 of stem `30 is provided with a key or slot so that it may be keyed to a valve spool 60. The valve spool is provided with a central longitudinal aperture 62 to receive the body portion of the stem. It is positioned thereon and may be held in place as by a set screw 63. The valve spool 60 is provided with a series of transverse annular grooves 65 separated by a plurality of transverse annular ridges 66. The assembly comprising the yoke, the threaded insert, the spool, and

4 the stem, as shown in FIGURE 2, together may be described as a moving or operatingelement of the valve, generally designated 100. It is understood of course that the extreme right hand end of stem 80, that is, the rst threaded portion 81, does not move, but is anchored to the coupling member 20 as has been described'Coupling member 20 may also be called the block since in addition to providing the coupling function at the right hand side as shown if FIGURE 1, it extends to form the interior of the entire valve in which the operating element is positioned.

The block 20 is provided with a central aperture 24 to receive the fixed channeled insert 50. This channeled insert is held in aperture 24 by retaining screw 26. The channeled insert 50 cooperates with the valve spool to channel the flow of fluid through the valve. In the embodiment shown in FIGURE 1, the valve spool is provided with a set of tive annular grooves 65, separated by ridges l66. The channeled insert 50 is provided with a central aperture 51 to receive the spool 60. The central aperture 51 of the insert 50 is provided with a set of live annular transverse grooves or channels 52, 53, 54, 55 and 56. These grooves are separated by raised ridges or lands in the same manner as the grooves 65 are separated by the ridges or lands 66, and the spacing of the grooves 52-56 corresponds with the spacing of the grooves 65. The ridges or lands of the spool and the insert contact each other with a sliding lit.

Certain of the annular grooves 52-56 communicate with external iluid communication lines as is described below. Thus, the grooves in the interior surface of the fixed channeled insert 50 communicate with bores or apertures through the insert which lead to the outer surface thereof so that communication is made to external lines. Channel 52 communicates with a pressure inlet line, not shown because it lies on a diterent diameter than the view taken. Channel 53 communicates with the longitudinal first output line 22 by means of the transverse connecting channel 22a. Groove 54 communicates with an exhaust or return line, not shown since it lies on a different diameter than the view taken. `Channel 55 communicates with the second output line 23 by means of connecting channel 23a. Channel 56 is connected to a pressure supply line, not shown. The spool 60 centers the yoke 72 with respect to the longitudinal axis of the spool -by means of its expanded left hand provided with splines 61 which slidably coact with corresponding grooves in the interior of the shaft portion 71 of yoke 72.

The valve 200 is shown in a central or neutral position in which no line communicates with any other line. If the spool moves to the right, which it may do because of the gap shown between magnets 32 and 33, channel 52 will communicate with channel 53, and channel 54 will communicate with channel 55. Thus, the pressure will be admitted to the first output line 22 and second output line 23 will be connected to the return line from channel 54. When the spool is moved an equal distance from neutral but to the left, that is, so that the magnets are twice as far apart as they are in the neutral position, channel 53 will be connected to channel 54, and channel 55 will be connected to channel 56. Thus, first output line 22 will be connected to the return line, and the second output line 23 will be connected to pressure. The cap member 40 is provided with a chamber 43 to enclose the operating element 100 and permitted to move therein without striking the wall of the cap member.

A second stage or operating valve generally designated is shown in a close-coupled position directly against coulping member 20. Coupling member 20" is provided with an aperture 25 to receive part of the second stage valve 90. The first output line 22 is continued to segment 22b, which is shown to turn downwardly and open into aperture 25. Second output line 23 continues to segment 2311 which is shown as an expanded portion opening to the righthand face of coupling member 20. It is apparent that the first and second output lines of valve 200 terminate close together on opposite sides of the aperture 25, and slightly displaced from each other with respect to the longitudinal direction along the valve 200. For reasons to be described below, this structure is valuable in transferring the high frequency output of rst stage or pilot valve 200 to control the second stage or operating valve 90 to take maximum advantage of the high frequency capabilities of the second stage of valve 90. To achieve this aspect of the present valves advantages, the second stage valve may have an actuating piston which actually extends partly into the body of coupling member of valve 200, and uses the interior of aperture 25 as part of its cylinder. A schematic representation of such an actuating piston is shown in phantom lines. It is seen that output line 22 ends in segment 22b on one side of the piston and output line 23 terminates in segment 23b which leads to the other side of the piston through a channel in the body of the second stage valve. Such a channel in the second stage valve is also shown schematically with dashed line. It is the structure of the described valve 200 which permits this type of possible coaction with a second stage valve.

The successful maximum high frequency response of valve 20|) is obtained when it is set as follows. The spool is positioned in its neutral position, as illustrated, and the adjustments as described, are made so that magnet 33 is spaced from magnet 32 a distance so that when the magnets are brought into contact, the valve will be in one of the communicating positions. It will be appreciated that the gap between the magnets resulting from the neutral position is exactly one-half the total longitudinal travel distance of magnet 33. That is, when the variable magnet has moved a further distance away from the fixed magnet equal to its neutral position distance, the valve will be in another communicating condition, reversed from the condition that exists when the magnets contact each other. With the spool in neutral position, the adjustments are made to provide the magnet gap as described, and the elements are then locked in place with the set screws as has been described. This adjustment is made with no magnetic forces being applied and it will therefore be appreciated that the spring portion 82 is in an unstressed condition. This is because the structure permits adjustment to be made of the yoke position without compressing or tensioning the spring 82.

Now, it is apparent that during operation, when xed flux magnet 32 is operated, and the eld in variable flux magnet 33 is such that it is attracted toward magnet 32, spring 82 is compressed a certain amount. When the ux in magnet 33 is such that it is repelled from magnet 32, and the spool has shifted to the left position, the spring 82 is under tension by the same amount that it Was previously under compression, since the travel to both sides of the unstressed position of the spring is the sarne. This provides a highly balanced yreturn bias due to the spring, regardless of which communicating position the valve is in. Because a single spring is used, the spring has a high rate, and the movement is relatively very small compared to the overall dimensions of the spring.

The major potrions of the operating elements of the valve are contained within the annulus of the fixed flux magnet 32. This structure has the advantage of permitting the use of the hydraulic fluid flowing through the Valve in its normal operation to be used as a cooling medium for the relatively large coil 32. The provision of such automatic cooling is valuable in that it keeps the current consumption lower, or alternatively, permits the use of a smaller magnet to obtain the required flux, since, it is well known, the magnet operates more eiciently if cooled.

The valve 200 can handle approximately tive gallons per minute of oil, at an input pressure of 3,000 p.s.i. with a drop of 1,000 p.s.i.l Its frequency of operation may be as high as 1,000 cycles per second. When used with a second stage or operating valve 90, which can be conventional in its structure except that it is operated by reversing the applied pressure and exhausts to the two sides of a single piston at one end thereof, such an operating valve may handle a flow of 200' gallons per minute at a frequency of up to 500 cycles per second.

The spring portion 82 may have a rate of 1,000 pounds per minute of oil, at an input pressure of 3,000 p.s.i. with on the spring during the operation of the valve is approximately 10 pounds. It is thus seen that the total travel of the yoke from the neutral position to one of the communicating positions may be on the order of approximately 100th of an inch.

The high speed frequency advantages of the present valve are due to an additive combination of several factors. The use of a single spring, relying on slight displacements on either side of its unstressed condition, means that are a balanced return force of either position is much more easily obtainable than can be achieved by attempting to set two different springs. The making of the rate of the spring very high, that is making the spring relatively stiff and heavy, compared to the total force the spring is expected to exert in either tension compression, insures that the balance restoring forces are equal and reliable. In this embodiment, it is seen for example that the total force required from the spring is of the order of 100th of the unit rate.

A very small throw involved contributes lto the high frequency response. The light Weight of the moving structure contributes to the response, and to this end, the perforated structure of the yoke 72 is important, as has been described. The small throws and consequent small dimensions permit most of the structure to be within the annulus of the magnet 32 as has been described. This in turn makes it possible to achieve the automatic cooling function with its desirable attributes as has been described.

The use of two magnets in the control permits a quicker response. lt also permits the step of setting the spacing at the neutral condition as has been described, since both magnets may of course lbe turned olf. The entire structure of the valve as described permits very short output lines to be brought to the boundary of the valve, terminating close together. This in turn permits their most intimate relationship with the operating piston of a cooperating second stage valve, as has been shown and described. Thus, as has been shown, the operating piston of a second stage valve may actually be introduced into the body of valve 200 and the output lines may be conducted to the opposite sides of this second stage valve operating piston. This structure, considered together minimizes the length of hydraulic line from the pilot valve to the second stage valve. The minimization of the quantity of oil and length of line at this point increases the effective transmission of the high frequency of valving. This structure also prevents a great difference in the length of the output lines, and this near approach to equal line length also increases the efficiency of the high frequency valving.

The length of the xed channeled insert may Vbe on the order of one and three quarter inches. The internal diameter of the xed flux magnet 32 annulus may be on the order of one and three quarter inches. The total length of the stem may be approximately three and one-quarter inches, its diameter approximately one-eighth inch, and the length of the spring portion 82 approximately one-half inch. These dimensions are not in themselves necessarily critical, but are given to provide a context to place this valve in its appropriate field of art.

We claim:

1. A high frequency valve comprising a fixed flux electromagnet in the shape of an annulus,

an operating element having a major portion thereof within said annulus, said operating element comprising a stem, said stem including a screw portion, a spring portion and a body portion joined together,

a valve spool disposed within said annulus axed to said body portion, a yoke adjustably fixed to one erd of said stem, the other end of said stem being affixed to said electromagnet, said yoke being positioned outside of said annulus, a variable flux annular electromagnet mounted on said yoke and opposing said xed flux electromagnet,

a plurality of channels and lines in said valve inside said annulus, said channels being selectively intercommunica'ing depending on the position of said spool with respect thereto,

said spring portion being unstressed when said spool is in a neutral position blocking intercommunication of said channels, said spring exerting a tension force when said spool is in a position on one side of said neutral position to intercommunicate certain said channels, and said spring exerting an equal compressive force when said spool is in a position on the other side of said neutral position to interconnect others of said channels.

2. A high frequency valve as set forth in claim 1 in which said spring portion and body portion are formed from a one piece stem and the unit rate of said spring portion being high compared to the total compressive bore tension force to be exerted by said spring portion.

3. A high frequency valve set `forth in claim 2 wherein said yoke comprises a generally circular member and said variable flux electromagnet is affixed to the outer rim thereof, and the center of said yoke comprises a shaft, and said shaft is affixed to said stem by Vernier adjusting means.

4. A high frequency valve as set forth in claim 3 wherein said Vernier adjusting means comprise a rotatable insert, threaded externally and internally, said external threads cooperating with matching threads on the interior of said shaft, and said internal threads cooperating with matching threads on the end of the said stem, said set of external threads and said set of internal threads differing in pitch so that when only insert is rota-ted, one set of threads moves said yoke in one direction and the other set of threads tends to move said yoke in the opposing direction at a different speed.

5. A high frequency valve as set forth in claim 4, wherein a first output line, a second output line, a pressure line and a return line are provided in said valve, said lines being selectively intercommunicating wiih certain 8 of said channels, said intercommunication depending on the position of said valve spool.

6. A high frequency valve as set forth in claim 5 wherein when said valve spool is in said neutral position, neither of said output lines communica-tes with any of said channels, when said valve spool is in a position so that said spring is under its maximum tension one of said output lines communicates with a pressure line and the other output line communicates wi'h a return line, and when said spool is in a position so that said spring is in i s maximum compression, the first mentioned said output line is connected to a return line and said second men- -tioned output line is connected to a pressure line.

7. A high-frequency valve asset forth in claim 6 wherein a coupling member is provided at one end. of .said valve, a recess is provided in a face of said coupling `member and both of said output.lines terminate close together on opposite sides of said recess. f t

S. A high frequency valve as set forth in claim 7 in combination wilh a second stage valve to be controlled by said high frequency valve, Said second stage valvebeing coupled to said face of said coupling member, said second stage valve having a single actuating piston extending at least partly into said recess in said face, one of said output lines communicating to one face of said piston, and the other of said output lines communicating to the other face of said piston.

References Cited UNITED STATES PATENTS 1,295,316 2/1919 Hines.

2,485,280 10/1949 Grace.

1,512,805 10/1924 Roucka 137-330 XR 2,904,075 9/1959 Markson 137-625.63 XR 3,040,768 6/1962 Pippenger 137-330 3,059,663 10/1962 Whitenack 137-330 3,099,280 7/1963 Holzbock 137-625.65 XR HENRY T. KLINKSIEK, Primary Examiner U.S. Cl. X.R.

Disclaimer and Dedication 3,466,003.Julz'u8 C'. Boonshaft, Huntingdon Valley and Kenneth W. Zeuncr, Newton, Pa. HIGH FREQUENCY VAL Patent dated Sept. 9, 1969. Disclaimer and dedication led Feb. 4, 1970, by the assignee, Weston I mtmments, I frw. Hereby enters this disclaimer to the entire remaining term of said patent and dedicates the patent to the Public.

[Official Gazette May 936', 1.970.] 

